FIRMAMENT, the sky, the heavens. In the Vulgate the word firmamentum, which means in classical Latin a strengthening or support (firmare, to make firm or strong) was used as the equivalent of (Gr., to make firm or solid) in the LXX., which translates the Heb. raqiya'. The Hebrew probably signifies literally "expanse," and is thus used of the expanse or vault of the sky, the verb from which it is derived meaning "to beat out." In Syriac the verb means "to make firm," and is the direct source of the Gr. and the Lat. firmamentum. In ancient astronomy the firmament was the eighth sphere containing the fixed stars surrounding the seven spheres of the planets.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)